C++ placement new not compatible with boost allocator

  allocator, boost, c++, c++11, stl

I’m using Boost.Interprocess shared memory, and I’m using interprocess Allocator with some STL compatible containers, when it comes to placement new, the code won’t compile since placement new expect void * while boost::interprocess::allocator::pointer can’t not be converted to void *.

below is a code to reproduce this


#include <memory>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/managed_shared_memory.hpp>
namespace ipc = boost::interprocess;

typedef ipc::allocator<int, ipc::managed_shared_memory::segment_manager> ShmemAllocator;

int main() {
    struct shm_remove {
      shm_remove() { ipc::shared_memory_object::remove("MySharedMemory"); }
      ~shm_remove() { ipc::shared_memory_object::remove("MySharedMemory"); }
    } remover;
  ipc::managed_shared_memory segment(ipc::open_or_create, "MySharedMemory", 1024 * 1024 * 10);

  ShmemAllocator shm_alloc(segment.get_segment_manager());
  ShmemAllocator::pointer shm_ptr = shm_alloc.allocate(1);

  std::allocator<int> std_alloc;
  std::allocator<int>::pointer std_ptr = std_alloc.allocate(1);
  
  new(std_ptr) int(3);
  new(shm_ptr) int(3); // this line doesn't work

  return 0;
}

the compile error I got:

/home/ziqi.liu/ClionProjects/shared_memory_experiment/src/main_a.cpp: In function ‘int main()’:
/home/ziqi.liu/ClionProjects/shared_memory_experiment/src/main_a.cpp:22:21: error: no matching function for call to ‘operator new(sizetype, boost::interprocess::allocator<int, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >::pointer&)’
   new(shm_ptr) int(3); // this line doesn't work
                     ^
In file included from /usr/include/c++/5/ext/new_allocator.h:33:0,
                 from /usr/include/x86_64-linux-gnu/c++/5/bits/c++allocator.h:33,
                 from /usr/include/c++/5/bits/allocator.h:46,
                 from /usr/include/c++/5/memory:63,
                 from /home/ziqi.liu/ClionProjects/shared_memory_experiment/src/main_a.cpp:1:
/usr/include/c++/5/new:111:7: note: candidate: void* operator new(std::size_t)
 void* operator new(std::size_t) _GLIBCXX_THROW (std::bad_alloc)
       ^
/usr/include/c++/5/new:111:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/5/new:119:7: note: candidate: void* operator new(std::size_t, const std::nothrow_t&)
 void* operator new(std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
       ^
/usr/include/c++/5/new:119:7: note:   no known conversion for argument 2 from ‘boost::interprocess::allocator<int, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >::pointer {aka boost::interprocess::offset_ptr<int, long int, long unsigned int, 0ul>}’ to ‘const std::nothrow_t&’
/usr/include/c++/5/new:129:14: note: candidate: void* operator new(std::size_t, void*)
 inline void* operator new(std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
              ^
/usr/include/c++/5/new:129:14: note:   no known conversion for argument 2 from ‘boost::interprocess::allocator<int, boost::interprocess::segment_manager<char, boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>, boost::interprocess::iset_index> >::pointer {aka boost::interprocess::offset_ptr<int, long int, long unsigned int, 0ul>}’ to ‘void*’
In file included from /home/ziqi.liu/.tspkg/include/boost/interprocess/mem_algo/detail/mem_algo_common.hpp:35:0,
                 from /home/ziqi.liu/.tspkg/include/boost/interprocess/allocators/detail/allocator_common.hpp:35,
                 from /home/ziqi.liu/.tspkg/include/boost/interprocess/allocators/allocator.hpp:30,
                 from /home/ziqi.liu/ClionProjects/shared_memory_experiment/src/main_a.cpp:2:
/home/ziqi.liu/.tspkg/include/boost/container/detail/placement_new.hpp:24:14: note: candidate: void* operator new(std::size_t, void*, boost_container_new_t)
 inline void *operator new(std::size_t, void *p, boost_container_new_t)
              ^
/home/ziqi.liu/.tspkg/include/boost/container/detail/placement_new.hpp:24:14: note:   candidate expects 3 arguments, 2 provided
CMakeFiles/main_a.dir/build.make:62: recipe for target 'CMakeFiles/main_a.dir/src/main_a.cpp.o' failed
make[2]: *** [CMakeFiles/main_a.dir/src/main_a.cpp.o] Error 1
CMakeFiles/Makefile2:162: recipe for target 'CMakeFiles/main_a.dir/all' failed
make[1]: *** [CMakeFiles/main_a.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

I’m sure there must a way to do this, since boost own containers are all compatible with boost::interprocess::allocator::pointer, but I’m not sure how they did it……I guess I should look for an alternative for placement new?

Source: Windows Questions C++

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